In my books, I like placing familiar historical figures in strange circumstances: Degas in New Orleans, Henry Adams in Japan. The great thing about writing non-fiction is that it doesn’t have to be remotely plausible, it just has to be true. In my new book, A Summer of Hummingbirds, I’ve drawn a looping (and maybe a little loopy) historical narrative around two eccentric artists: the stay-at-home poet Emily Dickinson and the nomadic painter of hummingbirds Martin Johnson Heade. On page 99, you’ll find me trying to figure out what makes Heade’s paintings of hummingbirds so magically vivid. Heade aspired to be the Audubon of hummingbirds; during the Civil War, he spent a few months in Brazil, where he wanted to experience the hummingbird habitat firsthand. His paintings of hummingbirds are almost shockingly immediate; they’re also highly sexual and sometimes a little gothic in their evocation of how life breeds on death. I found myself thinking about other bird painters in America, and I discovered that three of the greatest among them—the eighteenth-century explorer William Bartram, Audubon, and Heade—all (as I write on page 99) “came of age in Quaker settlements on the outskirts of Philadelphia.” All three artists, I concluded, “adopted some of the reverential and visionary attitude of the Quakers toward the natural world”—even when, as in the case of Bartram, they were handling rattlesnakes. Since I myself was born a Quaker on the outskirts of Philadelphia, page 99 has a very personal feel for me.